1. Field of the Invention
The present invention relates, in general, to a method for producing anti-Escherichia coli O157:H7 antibodies and, more particularly, to an improvement in the prevention of food toxication caused by E. coli O157:H7, along with the method.
2. Description of the Prior Art
First found in U.S.A. in 1982, Escherichia coli O157 is a kind of an enteropathogenic E, coli which inhabits the intestinal tract of humans or animals causing diarrhea and abdominal pain. On the whole, persons who are infected with Escherichia coli O157 usually suffer from hemorrhagic diarrhea. High similarity in shape and size makes it difficult to discriminate the bacteria of interest from typical coliform bacteria via morphological observation. Usually, identification of the bacteria of interest is attained by a serological method in which specific agglutination between antibody and antigen is utilized. In this regard, the taxonomic indicator characteristic of the enteric bacteria of interest is a protein which stands No. 157 in the discovery order of the protein O type antigens which have been found on the surface of Escherichia coli bacteria, so it is called O157 or O-157.
Escherichia coli O157 is very highly infectious. Generally, this pathogenic bacteria does not cause an attack of a disease without passage of a period of as long as 3.1-8 days after the infection. The long latent period makes it difficult to trace the cause of the infection and to prevent its diffusion. Once infecting human bodies, the pathogenic bacteria produces vero toxin, like dysenteric bacteria, causing abdominal pain and hemorrhagic diarrhea. In addition to breaking red blood cells in the body, the toxic protein attacks the kidney resulting in kidney failure, leading to hemolytic uremia. This disease develops complications in the nervous system, the respiratory system, and the circulatory system and may result in death. Its mortality is found to reach as high as 5-10%. Irrespective of ages, persons, whether they are weak or healthy, can be infected with and seriously afflicted by Escherichia coli O157.
In an epidemiological view, E. coli O157:H7 usually infiltrates humans through contaminated foods. For example, foods, such as water, ground beef, vegetables, etc, which are contaminated with animal or human excretes, are good intermediate media for the bacteria when not being heated at over about 65.degree. C. Actually, E. coli-attributable food poisoning occurred in a mass of elementary school children in 1996, Japan, raising a great social trouble. In America, E. coli O157:H7 is widely recognized as a food-poisoning cause to the general public. According to Center for the control of Disease of U.S.A., E. coli O157 in ground beef hamburgers is not killed, but causes food toxication when they are cooked at insufficiently high temperatures. Also, it is reported that as many as 20,000 food toxication cases are annually generated, leading 200-500 persons to death.
A reference directed to the detection of E. coli O157 is Korean Pat. Laid-Open Publication No. 99-68868, entitled "Monoclonal antibody for detecting Escherichia O157:H7 and its use", in which an immunological diagnosis method using monoclonal antibodies is used to determine rapidly and accurately whether the contamination with E. coli O157:H7 occurs. Another detection method for E. coli O157 is disclosed in Korean Pat. Laid-Open Publication No. 99-65107, entitled "Method for simultaneously detecting heterogenous genes of E. coli O157:H7 using polymerase chain reaction", in which four genes specific for the pathogenic bacteria (two vero toxins, a pathogenic factor attaching to cell walls, and an enzyme-specific gene) are detected by use of PCR. In addition to recognizing the presence of E. coli O157:H7 in meat, these methods can be applied for humans and animals. However, these methods are directed to the detection of E. coli O157, but not to the production of antibodies against E. coli O157.
Conventionally, antibodies have been produced by use of the blood of mammals such as sheep, goats, mice, rabbits, rats, etc. Use of mammalian blood in antibody production, however, always meets with the resistance of environmental organizations or animal rights protection agencies, resulting in low production yield and high cost. As an antigen for eliciting antibodies against E. coli O157:H7, the bacteria itself is used after being killed. Alternatively, antigenic materials which are isolated from the bacterial cell membranes are used However, neither of the methods are suitable to be applied for industrialization. For example, the former method is problematic of resulting in a weak binding of antibodies to the antigen. On the other hand, the latter method requires a great deal of time in isolating the antigenic materials, showing economical unfavorableness.
Limited as it is, the production of antibodies in birds has been utilized. From some points of view, antibody production is more advantageous in birds rather than in mammals. For instance, antibodies (IgY) produced in hens are transferred to eggs and then to chickens hatched therefrom as in mammals whose antibodies (IgG) are transferred from mothers to fetuses. The antibody concentration in the yolk of an egg is higher than or as high as in the blood of the hen. Indeed, the antibodies contained in 300 ml of the blood of a hen which lays 20 eggs in a month are as many as those contained in the eggs. More antibodies can be obtained from the eggs by six to seven times than from 40-50 ml of the blood of a rabbit.